(1) In Greek philosophy the word originally signified "investigation by dialogue", instruction by question and answer, as in the heuristic method of Socrates and the dialogues of Plato. The word dialectics still retains this meaning in the theory of education.

(2) But as the process of reasoning is more fundamental than its oral expression, the term dialectic came to denote primarily the art of inference or argument. In this sense it is synonymous with logic. It has always, moreover, connoted special aptitude or acuteness in reasoning, "dialectical skill"; and it was because of this characteristic of Zeno's polemic against the reality of motion or change that this philosopher is said to have been styled by Aristotle the master or founder of dialectic.

(3) Further, the aim of all argumentation being presumably the acquisition of truth or knowledge about reality, and the process of cognition being inseparably bound up with its content or object, i.e. with reality, it was natural that the term dialectic should be again extended from function to object, from thought to thing; and so, even as early as Plato, it had come to signify the whole science of reality, both as to method and as to content, thus nearly approaching what has been from a somewhat later period universally known as metaphysics. It is, however, not quite synonymous with the latter in the objective sense of the science of real being, abstracting from the thought processes by which this real being is known, but rather in the more subjective sense in which it denotes the study of being in connection with the mind, the science of knowledge in relation to its object, the critical investigation of the origin and validity of knowledge as pursued in psychology and epistemology. Thus Kant describes as "transcendental dialectic" his criticism of the (to him futile) attempts of speculative human reason to attain to a knowledge of such ultimate realities as the soul, the universe, and the Deity ; while the monistic system, in which Hegel identified thought with being and logic with metaphysics, is commonly known as the " Hegelian dialectic".

A. THE DIALECTIC METHOD IN THEOLOGY

[For dialectic as equivalent to logic , see art. LOGIC, and cf. (2) above. It is in this sense we here speak of dialectic in theology.] The traditional logic, or dialectic, of Aristotle's "Organon"--the science and art of (mainly deductive ) reasoning--found its proper application in exploring the domain of purely natural truth, but in the early Middle Ages it began to be applied by some Catholic theologians to the elucidation of the supernatural truths of the Christian Revelation. The perennial problem of the relation of reason to faith, already ably discussed by St. Augustine in the fifth century, was thus raised again by St. Anselm in the eleventh. During the intervening and earlier centuries, although the writers and Fathers of the Church had always recognized the right and duty of natural reason to establish those truths preparatory to faith, the existence of God and the fact of revelation, those praeambula fidei which form the motives of credibility of the Christianreligion and so make the profession of the ChristianFaith a rationabile obsequium , a "reasonable service", still their attitude inclined more to the Crede ut intelligas (Believe that you may understand) than to the Intellige ut credas (understand that you may believe ); and their theology was a positive exegesis of the contents of Scripture and tradition. In the eleventh and twelfth centuries, however, rational speculation was applied to theology not merely for the purpose of proving the praeambula fidei, but also for the purpose of analysing, illustrating and showing forth the beauty and the suitability of the mysteries of the ChristianFaith . This method of applying to the contents of Revelation the logical forms of rational discussion was called "the dialectic method of theology ". Its introduction was opposed more or less vigorously by such ascetic and mystic writers as St. Peter Damian, St. Bernard, and Walter of St. Victor ; chiefly, indeed, because of the excess to which it was carried by those rationalist and theosophist writers who, like Peter Abelard and Raymond Lully, would fain demonstrate the Christian mysteries, subordinating faith to private judgment. The method was saved from neglect and excess alike by the great Scholastics of the thirteenth century, and was used to advantage in their theology. After five or six centuries of fruitful development, under the influence, mainly, of this deductive dialectic, theology has again been drawing, for a century past, abundant and powerful aid from a renewed and increased attention to the historical and exegetical studies that characterized the earlier centuries of Christianity.

B. DIALECTIC AS FUNDAMENTAL PHILOSOPHY OF HUMAN KNOWLEDGE

[cf. (3) above]

(1) The Platonic Dialectic

From the beginnings of Greek philosophy reflection has revealed a twofold element in the contents of the knowing human mind : an abstract, permanent, immutable element, usually referred to the intellect or reason ; and a concrete, changeable, ever-shifting element, usually referred to the imagination and the external senses. Now, can the real world possess such opposite characteristics? Or, if not, which set really represents it? For Heraclitus and the earlier Ionians, stability is a delusion; all reality is change-- panta hrei . For Parmenides and the Eleatics, change is delusion; reality is one, fixed, and stable. But then, whence the delusion, if such there be, in either alternative? Why does our knowledge speak with such uncertain voice, or which alternative are we to believe ? Both, answers Plato, but intellect more than sense. What realities, the latter asks, are revealed by those abstract, universal notions we possess of being, number, cause, goodness, etc., by the necessary, immutable truths we apprehend and the comparison of those notions? The dialectic of the Platonic "Ideas" is a noble, if unsuccessful, attempt to answer this question. These notions and truths, says Plato, have for objects ideas which constitute the real world, the mundus intelligibilis , of which we have thus a direct and immediate intellectual intuition. These beings, which are objects of our intellectual knowledge, these ideas, really exist in the manner in which they are represented by the intellect, i.e. as necessary, universal, immutable, eternal, etc. But where is this mundus intelligibilis? It is a world apart ( choris ), separate from the world of fleeting phenomena revealed to the senses. And is this latter world, then, real or unreal? It is, says Plato, but a shadowy reflex of reality, a dissolving-view of the ideas, about which our conscious sense-impressions can give us mere opinion ( doxa ), but not that reliable, proper knowledge ( episteme ) which we have of the ideas. This is unsatisfactory. It is an attempt to explain an admitted connection between the noumenal and the phenomenal elements in knowledge by suppressing the reality of the latter altogether. Nor is Plato any more successful in his endeavour to show how the idea, which for him is a really existing being, can be at the same time one and manifold, or, in other words, how it can be universal, like the mental notion that represents it.

(2) Aristotelean and Scholastic Dialectic

Aristotle taught, in opposition to his master Plato, that these " ideas " or objects of our intellectual notions do not exist apart from, but are embodied in, the concrete, individual data of sense. It is one and the same reality that reveals itself under an abstract, universal, static aspect to the intellect, and under a concrete, manifold, dynamic aspect to the senses. The Christian philosophers of the Middle Ages took up and developed this Aristotelean conception, making it one of the cardinal doctrines of Scholastic philosophy, the doctrine of modern Realism. The object of the abstract, universal notion, they taught, is real being; it constitutes and is identical with the individual data of sense-knowledge; it is numerically multiplied and individualized in them, while it is unified as a class-concept or universal notion ( unum commune pluribus ) by the abstractive power of the intellect which apprehends the element common to the individuals of a class without their differentiating characteristics. The universal notion thus exists as universal only in the intellect, but it has a foundation in the individual data of sense, inasmuch as the content of the notion really exists in these sense-data, though the mode of its existence there is other than the mode in which the notion exists in the intellect : universale est formaliter in mente, fundamentaliter in re . Nor does the intellect, in thus representing individual phenomena by universal notions, falsify its object or render intellectualknowledge unreliable; it represents the Real inadequately, no doubt, not exhaustively or comprehensively, yet faithfully so far as it goes; it does not misrepresent reality, for it merely asserts of the latter the content of its universal notion, not the mode (or universality) of the latter, as Plato did.

But if we get all our universal notions, necessary judgments, and intuitions of immutable truth through the ever-changing, individual data of sense, how are we to account for the timeless, spaceless, changeless, necessary character of the relations we establish between these objects of abstract, intellectual thought: relations such as "Two and two are four", "Whatever happens has a cause", "Vice is blameworthy"? Not because our own or our ancestors' perceptive faculties have been so accustomed to associate certain elements of consciousness that we are unable to dissociate them (as materialist and evolutionist philosophers would say); nor yet, on the other hand, because in apprehending these necessary relations we have a direct and immediate intuition of the necessary, self-existent, Divine Being (as the Ontologists have said, and as some interpret Plato to have meant); but simply because we are endowed with an intellectual faculty which can apprehend the data of sense in a static condition and establish relations between them abstracting from all change.

By means of such necessary, self-evident truths, applied to the data of sense-knowledge, we can infer that our own minds are beings of a higher (spiritual) order than material things and that the beings of the whole visible universe --ourselves included--are contingent, i.e. essentially and entirely dependent on a necessary, all-perfect Being, who created and conserves them in existence. In opposition to this creationist philosophy of Theism, which arrives at an ultimate plurality of being, may be set down all forms of Monism or Pantheism, the philosophy which terminates in the denial of any real distinction between mind and matter, thought and thing, subject and object of knowledge, and the assertion of the ultimate unity of being.

(3) The Kantian Dialectic

While Scholastic philosophers understand by reality that which is the object directly revealed to, and apprehended by, the knowing mind through certain modifications wrought by the reality in the sensory and intellectual faculties, idealist or phenomenalist philosophers assume that the direct object of our knowledge is the mental state or modification itself, the mental appearance , or phenomenon , as they call it; and because we cannot clearly understand how the knowing mind can transcend its own revealed, or phenomenal, self or states in the act of cognition, so as to apprehend something other than the immediate, empirical, subjective content of that act, these philosophers are inclined to doubt the validity of the "inferential leap" to reality, and consequently to maintain that the speculative reason is unable to reach beyond subjective, mental appearances to a knowledge of things-in-themselves. Thus, according to Kant, our necessary and universal judgments about sense-data derive their necessity and universality from certain innate, subjective equipments of the mind called categories, or forms of thought, and are therefore validly applicable only to the phenomena or states of sense-consciousness. We are, no doubt, compelled to think of an unperceived real world, underlying the phenomena of external sensation, of an unperceived real ego , or mind, or soul, underlying the conscious flow of phenomena which constitute the empirical or phenomenal ego , and of an absolute and ultimate underlying, unconditioned Cause of the ego and the world alike; but these three ideas of the reason --the soul, the world, and God --are mere natural, necessary products of the mental process of thinking, mere regulative principles of thought, devoid of all real content, and therefore incapable of revealing reality to the speculative reason of man. Kant, nevertheless, believed in these realities, deriving a subjective certitude about them from the exigencies of the practical reason, where he considered the speculative reason to have failed.

(4) The Hegelian Dialectic

Post-Kantian philosophers disagreed in interpreting Kant. Fichte, Schelling, and Hegel developed some phases of his teaching in a purely monistic sense. If what Kant called the formal element in knowledge --i.e. the necessary, universal, immutable element--comes exclusively from within the mind, and if, moreover, mind can know only itself, what right have we to assume that there is a material element independent of, and distinct from, mind ? Is not the content of knowledge, or in other words the whole sphere of the knowable, a product of the mind or ego itself? Or are not individual human minds mere self-conscious phases in the evolution of the one ultimate, absolute Being? Here we have the idealistic monism or pantheism of Fichte and Schelling. Hegel's dialectic is characterized especially by its thoroughgoing identification of the speculative thought process with the process of Being. His logic is what is usually known as metaphysics : a philosophy of Being as revealed through abstract thought. His starting-point is the concept of pure, absolute, indeterminate being; this he conceives as a process, as dynamic. His method is to trace the evolution of this dynamic principle through three stages:

the stage in which it affirms, or posits, itself as thesis;

the stage of negation, limitation, antithesis, which is a necessary corollary of the previous stage;

the stage of synthesis, return to itself, union of opposites, which follows necessarily on (l) and (2).

Absolute being in the first stage is the idea simply (the subject-matter of logic ); in the second stage (of otherness) it becomes nature (philosophy of nature ); in the third stage (of return or synthesis) it is spirit (philosophy of spirit-- ethics, politics, art, religion, etc.).

Applied to the initial idea of absolute Being, the process works out somewhat like this: All conception involves limitation, and limitation is negation; positing or affirming the notion of Being involves its differentiation from non-being and thus implies the negation of being. This negation, however, does not terminate in mere nothingness; it implies a relation of affirmation which leads by synthesis to a richer positive concept than the original one. Thus: absolutely indeterminate being is no less opposed to, than it is identical with, absolutely indeterminate nothing: or BEING-NOTHING; but in the oscillation from the one notion to the other both are merged in the richer synthetic notion, of BECOMING.

This is merely an illustration of the a priori dialectic process by which Hegel seeks to show how all the categories of thought and reality (which he identifies) are evolved from pure, indeterminate, absolute, abstractly-conceived Being. It is not an attempt at making his system intelligible. To do so in a few sentences would be impossible, if only for the reason, that Hegel has read into ordinary philosophical terms meanings that are quite new and often sufficiently remote from the currently accepted ones. To this fact especially is due the difficulty experienced by Catholics in deciding with any degree of certitude whether, or how far, the Hegelian Dialectic--and the same in its measure is true of Kant's critical philosophy also--may be compatible with the profession of the Catholic Faith. That these philosophies have proved dangerous, and have troubled the minds of many, was only to be expected from the novelty of their view-points and the strangeness of their methods of exposition. Whether, in the minds of their leading exponents, they contained much, or little, or anything incompatible with Theism and Christianity, it would be as difficult as it would be perhaps idle to attempt to decide. Be that as it may, the attitude of the Catholic Church towards philosophies that are new and strange in their methods and terminology must needs be an attitude of alertness and vigilance. Conscious of the meaning traditionally attached by her children to the terms in which she has always expounded those ultimate philosophico-religious truths that lie partly along and partly beyond the confines of natural human knowledge, and realizing the danger of their being led astray by novel systems of thought expressed in ambiguous language, she has ever wisely warned them to "beware lest any man cheat [them] by philosophy, and vain deceit" ( Colossians 2:8 ).

For the use of dialectic in the early Christian and medieval schools, see THE SEVEN LIBERAL ARTS.

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